JPS62114202A - Pressure sensitive conductive rubber sheet - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a pressure-sensitive conductive rubber sheet, and more specifically, it is a rubber sheet body with excellent rubber elasticity made by adding an inorganic filler to a rubber compound. In particular, the present invention relates to a pressure-sensitive conductive rubber sheet that has an improved sheet surface layer, has excellent creep resistance, and can be used repeatedly.

(Prior art) Conventionally, carbon black, which has excellent conductivity, was used as a rubber elastic body.
It is known, for example, in JP-A No. 55-58504 and JP-A No. 55-14, that when a rubber sheet mixed and filled with metal particles etc. is subjected to pressure deformation, the electrical resistance value decreases significantly.
This method has already been disclosed in Japanese Patent Application Laid-open No. 7549 and Japanese Patent Application Laid-Open No. 56-5840.

In addition, the surface layer of the pressure-sensitive conductive rubber sheet has a feature in which voids of cellular structure are formed in the surface layer of the sheet, and a rubber sheet is formulated with a high content of conductive material such as metal powder. , for example, is disclosed in Japanese Patent Application Laid-Open No. 58-209810. Furthermore, gold l71uIA fibers are embedded in the thickness direction of the rubber sheet (for example,
220307) and the like have been proposed.

(Problems to be Solved by the Invention) However, such a conductive rubber sheet with an improved surface layer has a structure in which the metal particles or metal fibers sink from the surface of the rubber matrix and have depressions on the surface. When no pressure is applied, the metal filler does not come into direct contact with the electrode plate, cutting off the current, while when pressure is applied, the electrode plate comes into contact with the metal filler due to the deformation of the rubber matrix, causing an electric circuit. is formed. However, minute foreign matter such as dust may get stuck in the minute depressions on the surface of the rubber matrix, which may prevent the electrical resistance value from decreasing when pressurized, resulting in poor sensitivity.

Moreover, after repeated use over a long period of time, the surface layer of the rubber sheet becomes fatigued and hardened, and it also lacks creep-resistant properties, and the electrode plate constantly contacts the conductive material located on the surface of the rubber matrix to form an electric circuit. This also has the disadvantage that it becomes impossible to increase the change in electrical resistance value when pressurized, resulting in a pressure-sensitive conductive rubber sheet with poor sensitivity.

The present invention addresses the above-mentioned circumstances and provides a pressure-sensitive conductive rubber sheet that can significantly reduce electrical resistance by pressurization, maintain creep resistance and fatigue resistance, and maintain good sensitivity over a long period of time. The purpose is to

(Means for Solving the Problems) That is, the present invention is characterized by a rubber having electrical insulation properties, a conductive carbon blank, and short fibers made of non-metallic inorganic material, powder, and whiskers. A conductive rubber sheet comprising: a sheet-like composite in which at least one inorganic filler comprising: be.

First, the pressure-sensitive conductive rubber sheet of the present invention will be explained in detail based on the accompanying drawings.

FIG. 1 is a longitudinal sectional view of a pressure-sensitive conductive rubber sheet of the present invention, and FIG. 2 is a longitudinal sectional view of a rubber sheet showing a modified embodiment of the present invention. A sheet-like composite (2) in which conductive carbon black and at least one inorganic filler selected from short fibers, powder, and whiskers made of non-metallic inorganic substances are mixed into an insulating rubber matrix. electrically insulating powder (4) on both surface layers (3) of the composite (2).
) is buried in the sheet-like composite (2).

On the other hand, the pressure-sensitive conductive rubber sheet (1) shown in FIG.
is buried.

The thickness of the surface layer (3) shown in FIGS. 1 and 2 above is 0.1 to 20% of the total thickness of the sheet-like composite (2).
%.

In the present invention, examples of the matrix rubber having electrical insulation properties include natural rubber, polybutadiene rubber, polyisoprene rubber, styrene-butadiene copolymer rubber, nitrile rubber, butyl rubber, silicone rubber, chloroprene rubber, acrylonitrile-butadiene rubber, etc. There are polymer rubbers, ethylene-propylene copolymer rubbers, etc., and it is also possible to use two types of these rubbers. In order to improve mechanical strength and heat resistance, the above-mentioned rubber is crosslinkable with sulfur, a sulfur compound, or a peroxide, or is used after being crosslinked.

Further, as the conductive carbon black used in the present invention, for example, commonly used ones such as furnace black type, acetylene black type, thermal black type, channel black light, etc. are used, and the amount added is 100 parts by weight of the above rubber. 2.0 to 100 parts by weight,
Preferably, the amount is 10 to 80 parts by weight, and if it is less than 2 parts by weight, the resistance value will be high both when pressurized and when not pressurized, and a pressurized conductive rubber will not be obtained.

On the other hand, if it exceeds 100 parts by weight, the rubber will harden and the change in resistance value due to pressurization will become smaller.

The inorganic filler used in the present invention is non-metallic inorganic short fibers, powder/body, or whiskers, and the short fibers are made of ceramic materials such as silicon carbide (SiC), glass, and silicon nitride (Si3N4). It has a length of 1 μm to 10 mm and a diameter of 0.3 to 30 μm,
On the other hand, the powder is called ceramic powder with a particle size of 0.05 μm to 100 μm, such as silicon carbide (SiC).
), titanium carbide (TiC), boron carbide (B4C),
Carbides such as tungsten carbide (WC), silicon nitride (Si
3N 4), nitrides such as aluminum nitride (AIN), boron nitride (BN), titanium nitride (TiN), alumina (ALI20-1), zirconia (Zr0)
2) An oxide such as Helia (Bed), most preferably silicon carbide or silicon nitride.

Furthermore, as whiskers, α-silicon carbide (α-5i
C), β-silicon carbide (β-3iC), silicon nitride (
Si3N 4), α-alumina (ALa03), titanium oxide, zinc oxide, tin oxide, graphite, Fes CuNi
etc., and the diameter is 0.05 to 3. um, length 5~5
It is a needle-like single crystal with a shape of about 00 μm. When adding the above-mentioned inorganic filler to rubber, it is possible to treat it with a silane coupling agent, a titanium coupling agent, etc. in advance, or to add a silane coupling agent or a titanium coupling agent at the time of mixing with the rubber. This further enhances the reinforcing effect and improves the dispersibility into rubber.

The amount of the inorganic filler added is 1 to 80 parts by weight, preferably 5 to 40 parts by weight, based on 100 parts by weight of rubber.
If the amount of the inorganic filler added is less than 1 part by weight, the resistance value when no pressure is applied will decrease, and the electrical resistance value will be high at a pressure of 0.5 kg/-, resulting in poor conductivity. If the temperature is exceeded, the hardening of the rubber will increase.

Further, the electrically insulating powder (4) used in the present invention includes glass, calcium carbonate, clay,
It is made of inorganic materials such as talc, or organic materials such as phenol resin, epoxy resin, urea resin, or ebonite, and its shape includes powder, granules, or small rods, and its diameter is 0.
It consists of 1-100 μm. The amount of the powder (4) added is 0.05 to 5% by weight, and if it is less than 0.05% by weight, the effect of the present invention cannot be expected, while if it exceeds 5% by weight, the hardness of the surface layer will increase. . As a result, the surface layer (3) of the pressure-sensitive conductive rubber sheet (1) has the electrically insulating powder (4) mixed and dispersed therein, so that the electrode plate in contact with it when no pressure is applied. An electrical circuit is not formed between the rubber sheet (1
) is compressed, so there is a high possibility that the surface N(3) and the conductive members dispersed in the inner layer will come into contact with each other (and a circuit will be formed).

Further, when the powder (4) is embedded in the surface layer (3) of the sheet, the coefficient of friction decreases as the adhesiveness of the surface decreases, and therefore the electrode plate becomes easier to separate from the surface of the rubber sheet.

It was also revealed that the pressure-sensitive conductive rubber sheet was further mechanically reinforced by the powder (4), resulting in less change in electrical resistance over time, and also less fatigue due to repeated pressurization. became.

The above-mentioned pressurized conductive rubber sheet (1) is made of electrically insulating rubber, conductive carbon plastic, inorganic filler, and if necessary, softeners, anti-aging agents, and vulcanization aids commonly used in rubber. , a crosslinking agent, etc., and knead these components using, for example, a Banbury mixer or kneader roll to form a sheet, and electrically insulating powder (4) is coated on the surface of this sheet. or by molding a sheet-like surface layer (3) mixed with electrically insulating powder (4) in advance, laminating it on the sheet body, and then vulcanizing it. Can be manufactured.

(Example) Next, the present invention will be explained in more detail using specific examples.

Example 1.2, Comparative Example 1.2 Based on the formulation shown in Table 1, the rubber compound was kneaded in a Banbury mixer and then extruded into a 2 mm thick sheet using a roll. After rubbing the electrically insulating glass powder shown in Table 1 onto both sides of the sheet, it was sandwiched between molds and press vulcanized under vulcanization conditions of 150° C. for 20 minutes. The obtained sheet was cut into 30 x 33 m111 pieces to make a test piece, and the initial electrical resistance value of this when no pressure was applied (however, a 100 g Teflon plate was placed on the test piece) or when pressurized was measured. It was measured. Also, the above sheet is 0.5k
After applying pressure 10 times under the pressure condition of g/cti,
The electrical resistance value of the sheet was measured when no pressure was applied and when a pressure of 0.5 kg/cIll was applied. The resistance value retention rate (%) after repeated pressurization 10 times is the value obtained by dividing the resistance value during processing by the resistance value when no pressure is applied.

In addition, in order to measure the degree of change in electrical resistance value, a gradually increasing load was applied to the above test piece discontinuously, and the electrical resistance value at that time was measured. Then, the load was removed, various loads were applied again, and the change curves of the electrical resistance values were determined for the second and third times. The results are shown in FIG.

Furthermore, in order to measure the creep resistance of the rubber sheet, a load of 0.5 kg/cd was applied to the sheet and the change in resistance value during creep was determined. These results are shown in Table 2.

To measure the electrical resistance value, first, the test piece was
At this time, a copper plate with a thickness of about 0.3 mm was installed between the test piece and the Teflon plate, and the resistance value was determined using a digital multimeter using this pair of copper plates as electrode plates. Pressurization was performed by placing a weight on the Teflon plate located on the upper side.

Table 2 *2 This is the value obtained by dividing the resistance value during creep (Rf) by the resistance value before creep (Ro).

As a result, a conductive rubber sheet in which the above glass powder is embedded in the surface of a rubber sheet mixed with carbon black and whiskers has a higher resistance when no pressure is applied than a conductive rubber sheet in which the above glass powder is not embedded in the surface. The resistance value is high, the resistance value change after pressurization is large, and the sensitivity is good, and the resistance value change is small even with repeated pressurization, and the hysteresis of the electrical resistance value is small. also has excellent creep resistance.

(Results of the Invention) As described above, the pressure-sensitive conductive rubber sheet of the present invention is obtained by mixing an inorganic filler selected from short fibers, powder, and whiskers in a rubber matrix in combination with carbon black. By embedding electrically insulating glass powder on both surfaces or one surface of the sheet, the electrical resistance value when no pressure is applied increases further and the insulating state is maintained.
On the other hand, in a pressurized state, the electrical resistance value decreases greatly and becomes conductive, and the change in resistance value is large (and the sensitivity is good. However, the change in electrical resistance value is small, and it has fatigue resistance and creep resistance, and has the effect of having a long life.

[Brief explanation of drawings]

FIG. 1 is a longitudinal cross-sectional view of a pressure-sensitive conductive rubber sheet according to the present invention, FIG. 2 is a longitudinal cross-sectional view of a sheet showing another modification of the pressure-sensitive conductive rubber sheet, and FIG. It is a figure which shows the change curve from the 1st time to the 3rd time obtained by plotting the change of the electrical resistance value with pressurization of the rubber sheet based on an example and a comparative example. (1) −−−−−・−・Pressure-sensitive conductive rubber sheet (2+
-m-・-- Sheet-like composite (3)・-1--・-・Surface layer f41---Glass powder Patent applicant Sannohoshi Belting Co., Ltd. Figure 1 Figure 3 0Ω01 0.01 0.1 1P
Ressure (kg/cm2) Procedural amendment (voluntary) 1. Indication of the case 1985 Patent Application No. 255652 2. Name of the invention Pressure-sensitive conductive rubber sheet 3. Person making the amendment Relationship to the case Patent applicant address 4-1-21 Hamazoe Dori, Nagata-ku, Kobe, Voluntary Amendment 5, Claims of the Specification Subject to Amendment and Detailed Explanation of the Invention Column (1) Amend the Claims of the Specification as per the attached sheet. . (2) "Inorganic filler" on page 1, line 18 of the specification is corrected to "inorganic filler." (3) "Can be used for a long period of time" on page 1, line 20 to page 2, line 1 of the specification is corrected to "can be used for a long period of time." (4) "Minute" on page 3, line 7 of the specification is corrected to "minimal". (5) Insert ", chlorosulfonated polyethylene, fluorine, silicone rubber, urethane elastomer, thermoplastic elastomer" after "ren copolymer rubber" on page 5, line 15 of the specification. (6) "Pressure conductive rubber" on page 6, line 7 of the specification is corrected to "pressure-sensitive conductive rubber." (7) Correct "length" on page 6, line 14 of the specification cylinder to "length". (8) Delete "The reinforcing effect is further enhanced" on page 7, lines 15-16 of the specification. (9) “There is little change” on page 9, line 8 of the specification.
"The changes are small." 00) "The above pressure-sensitive conductive rubber sheet +11 J" on page 9, line 10 of the specification is corrected to "the above-mentioned pressure-sensitive conductive rubber sheet 1)". (11) About 200 g on page 11, line 12 of the specification
j is corrected to "approximately 100 gJ." (■ "(Results of the invention)" on page 13, line 10 of the specification box is corrected to "(effects of the invention)." 7. List of attached documents (11 attachments, 1 copy) 2. Claim 1: Rubber having electrical insulation properties, a conductive carbon blank, and at least one inorganic filler selected from short fibers, powder, and whiskers made of non-metallic inorganic materials in a rubber matrix. A pressure-sensitive conductive rubber sheet, which is a dispersed sheet-like composite, and has electrically insulating powder embedded in at least one surface layer of the composite. 2. The above-mentioned inorganic material. The pressure-sensitive conductive rubber sheet according to claim 1, wherein the filler is a whisker.

Claims (1)

[Scope of Claims] 1. A rubber matrix containing electrically insulating rubber, conductive carbon black, and at least one inorganic filler selected from short fibers, powder, and whiskers made of nonmetallic inorganic materials. 1. A pressure-sensitive conductive rubber sheet, characterized in that it is a uniformly dispersed sheet-like composite, and electrically insulating powder is embedded in at least one surface layer of the composite. 2. The pressure-sensitive conductive rubber sheet according to claim 1, wherein the inorganic filler is a whisker.